Clamping and tensioning a sheet on a cylinder

ABSTRACT

To avoid wrinkles in blankets and die sheets on cylinder impression machines, a clamp arrangement is disclosed in which a multiplicity of spring-tensioned clamps on the roll pull continuously on one end of the blanket or die sheet through a toggle action. These toggles, one for each clamp, can be individually collapsed while the associated clamp is released from the blanket and then the grip of the clamp reapplied so as to equalize the tension with respect to the other clamps. The invention is described in connection with paper carton blanking using photo-etched die sheets which must register accurately between the impression rolls.

United States Patent [191 Steinmetz et al.

[451 Mar. 11, 1975 1 CLAMPING AND TENSIONING A SHEET ON A CYLINDER [73] Assignee: The Rotographic Machinery Company, Cockeysville, Md.

[22] Filed: Dec. 18, 1973 [21] Appl. No.: 425,910

Related US. Application Data [63] Continuation of Ser. No. 9,343, Feb. 6, 1970,

abandoned.

[52] US. Cl. Nil/415.1 [51] Int. Cl. B4lf 27/06, B4lf 7/22 [58] Field of Search ..101/415.1, 378

[56] References Cited UNITED STATES PATENTS 640,447 1/1900 Corbin 101/220 X 838,790 12/1906 Kneppler 101/415.l 1,260,470 3/1918 Smith et a1 101/4151 2,050,950 8/1936 Huck 2,089,225 8/1937 Polachek 101/226 ROTATION 2,103,617 12/1937 Gericke .1 101/4151 2,309,161 1/1943 Breman et a1. 101/4151 2,737,887 3/1956 Gericke 101/4151 3,151,553 10/1964 Norton 101/4151 3,203,346 8/1965 Norton et a1. [OI/415.1 X 3,456,587 7/1969 Hulen 101/4151 Primary Examiner-J. Reed Fisher Attorney, Agent, or Firm-Walter G. Finch [57] ABSTRACT To avoid wrinkles in blankets and die sheets on cylinder impression machines, a clamp arrangement is disclosed in which a multiplicity of spring-tensioned clamps on the roll pull continuously on one end of the blanket or die sheet through a toggle action. These toggles, one for each clamp, can be individually collapsed while the associated clamp is released from the blanket and then the grip of the clamp reapplied so as to equalize the tension with respect to the other clamps. The invention is described in connection with paper carton blanking using photo-etched die sheets which must register accurately between the impression rolls.

16 Claims, 14 Drawing Figures PATENTEUHARI um 3.869.985

SHEET 1 0F 7 FIG. 7.

WILL/AM F 77-1'OMS PATEHTED H AR I I 195 5 sumenn PATENTEU W1 1 I975 sum 3 0r 7 FIG. 3.

Mr lllllllllllm 42\ iwulmmlu l PATENTEDHARI 1 I975 FIG. 8.

ECCENTR/C/TY IOOL ' FIG. 9.

PATENTED MARI 1 1975 saw 7 or f! CLAMPING AND TENSIONING A SHEET ON A CYLINDER This is a continuation of application Ser. No. 9,343, filed Feb. 6, 1970, now abandoned.

This invention relates generally to flexible sheet securing devices for rotary cylinders, and more particularly to an arrangement for eliminating wrinkles in blankets and die sheets on cylinder impression machines.

In the packaging industry, large-diameter cooperating drums are used between which paper webs are fed. These drums carry blanket dies for slitting and creasing the web to form container blanks. The die normally consists of a male and female die arrangement using a special technique where the cutting is a pinch force or crushing action. The cutting elements are raised portions of a thin flexible sheet which must be very accurately positioned.

Prior drums, in addition to supporting the die sheet, were also required to have clamping fingers to pull the sheet of stock accurately through the die. The presence of these clamping fingers occupied space behind the leading edge clamp of the die itself and in order to minimize waste of the paper sheet, the distances had to be held to an extreme minimum.

This forced the design of the clamp arrangement to make a sharp bend in the leading edge of the sheet metal die blanket. lnvariably, this caused cracks to form and an ultimate early failure of those dies.

It is an object of this invention, therefore, to provide an improved clamping arrangement for dies which would require no sharp bends in the die blanket.

Another object of this invention is to provide a die blanket tensioning arrangement which has a multiplic' ity of clamping points, each individually applied and tensionable to more effectively remove wrinkles and bulges from the die blanket.

Yet another object of this invention is to provide adjustable mounting means for accurately positioning and securing a wrap-around member upon a rotary drum in a web-fed machine.

To provide a spring bias arrangement for a circumferential tension toggle on cylinder blankets, is still another object of this invention.

Other objects and attendant advantages of this inven tion will become more readily apparent and understood from the following detailed specification and accompanying sheets of drawings in which:

FIG. 1 is a perspective view showing the clamping arrangement ofthe present invention as applied to the die cylinders of a web-fed variable repeat cutter-creaser machine;

FIG. 2 is a detailed perspective view of one of the clamping and tensioning units for the die cylinders of the web-fed variable repeat cutter-creaser machine of FIG. I with a die positioned in readiness for installatron;

FIG. 3 is a section taken on line 3-3 of FIG. 2 showing the die applied and clamped but not tensioned;

FIG. 4 is a section taken on line 3-3 of FIG. 2 and similar to FIG. 3, but with the die under tension and ready for use;

FIG. 5 is an exploded perspective view of various elements of the movable trailing edge clamps;

FIG. 6 is a section through the trailing edge clamps in a locked, or clamped, condition;

FIG. 7 is a section similar to FIG. 6 through the trailing edge clamps but with the clamps unlatched;

FIG. 8 is a perspective view of a clamping block;

FIG. 9 is a section taken on line 9-9 of FIG. 2 showing details of an adjustable die-locating dowel;

FIG. 10 is a section taken along line l0-10 of FIG.

FIG. 11 is a detail, partly in section, and taken on line 1111 of FIG. 12;

FIG. 12 is an end elevation of a shifting mechanism for positioning the die;

FIG. 13 is a fragmentary detail showing the left-hand shifting mechanism for translating the clamp bar; and

FIG. 14 is a view taken on line 14-l4 of FIG. 12 showing the right-hand shifting mechanism.

Referring now to the details of the invention as shown first in FIG. 1, reference numberal 10 indicates generally a web-fed variable repeat cutter-creaser machine for use in the paper carton industry. This machine 10 has a pair of cylinders or drums 12 and 14 which rotate together cooperatively upon a continuous web of paper carton stock, not shown, fed between them.

Each drum l2 and 14 has a leading edge 16 relative to rotation directions as shown in FIG. 4, which defines the position to be occupied by the first edge of a cutting die 114 to be affixed about the drum 14. The trailing edge ofeach drum l2 and 14 is shown by reference numeral 18.

A multi-element clamping and tensioning means 20 bridges the gap between these positions of the leading and trailing edges 16 and 18 of each drum l2 and 14. This clamping and tensioning means 20 occupies a flat 22 machined across each drum 12 and 14 so as to lie below their peripheries as best shown in FIG. 2. Only one element of the clamping and tensioning means 20 is shown in FIG. 2 for clarity, but in a typical arrangement these elements may total nineteen across each drum as shown in FIG. 1. The number of elements of the clamping and tensioning means 20 utilized, however, will depend on the requirements of a particular machine 10.

In addition to the flat 22 and adjacent thereto, there is machined a leading edge cutout and a trailing edge cutout in the drum, reference numerals 24 and 26 respectively. The drums l2 and 14 are hollow, with each drum being provided with a large bore 28.

A clamping bar extends across the length of each drum l2 and 14 and it is seated in the cutout 24 and it is secured there with bolts 32. It is also secured at locations one-third and two-thirds across the length thereof by screws where the gap occurs between clamping elements. These bolts 32 pass through longitudinally elongated slots 34 intermediate the ends of the bar 30.

Each toggle-like element of the clamping and tensioning means 20 as shown in FIGS. 2 and 3, is a toggle joint and is dependent from the bar 30 by means which includes a leading edge clamping mechanism 36L. A pair of links comprising a bifurcated link 38 and a tensioning linkage 40 extend to a trailing edge clamping mechanism 36T.

Instead of joining to another long bar at this end, short individual clamp bars 64 are used. The links 40 articulate on a hinge bolt 44 which passes through a tongue 42 on the bifurcated link 38.

The tongue 42 is also provided with an-extending boss 46 shown in FIG. 3 which receives the end of a long compression coiled spring 50 that is housed in a tube 48 and backs up against the far wall of the bore 28 and thus act as a substantially radially acting biasing means.

As shown in FIG. 4, this spring 50 normally urges the pair of links 38, 40 radially outwardly from the drum 14 or drum 12 as the case may be. The linkage can be collapsed and held to the flat 22, the links 38 and 40 being co-linear in this position by means of a quarter turn screw 52 which is secured in a threaded hole 54 as best shown in FIGS. 2 and 3.

Short individual hinge brackets 58 are fastened to the drum 14 within the trailing edge cutout 26 with bolts 60, as shown best in FIGS. 2, 3, 4 and 5, and each has a transverse hole 62. Narrowed portions 66 of the clamp bars 64 pivot here on hinge pins 68.

The leading edge and trailing edge clamping mechanisms 36L and 36T are similar. Each mechanism 36L and 36T is provided with a pair of side plates 70. At the trailing edge of mechanism 36T, these plates 70 are bolted to the hinged clamp bars 64, while at the leading edge of the mechanism 36L, they are bolted to the fixed clamp bar using bolts 74.

As shown in FIG. 5, a hole 72 in the plate 70 is provided to receive this bolt 74 which extends through to engage a threaded hole 76 in the clamp bar 64.

Each plate 70 is provided with a pair of holes 78 and 80 diagonally opposed from each other and another hole 82 in an intermediate corner, as best shown in FIG. 5. The holes 78 receives a pin 92 extending from the side of a clamping block 84T (or 84L).

The hole 80 receives a pin 104 extending from the side ofa T-shaped latch 102. The remaining hole 82 engages a pin 112 near the end of the tensioning link 40. Thus articulated, the clamping block 84T presents a nose 86T having a safety flange 90T to a clamping surface 88T on the clamp bar 64.

In the same way, as shown in FIG. 2, the clamping block 84L presents a nose 86L to a clamping surface 88L on the clamp bar 30 in the case of the leading edge clamping mechanism 36L.

In both cases, the confronting nose and surface are normally biased together by means of coiled compression springs 96, 98 housed at one end in a pocket 94, as shown best in FIGS. 6, 7, and 8, of the clamping block. At the other end, the springs 96, 98 are received in a pocket 100L in the bar 30 and in an opposing pocket 100T of the bar 64.

As shown best in FIGS. 6 and 7, a camming surface 106 is provided on the latch 102 as well as a tool socket 108. A rod-like tool 110 can be inserted in the socket 108 to rotate the latch 102 approximately 90 about hinge pin 104 from the position in FIG. 6 to the position in FIG. 7. This action compresses the springs 96 and 98 and separates the confronting nose 86T (or 86L) and clamping surface 8ST (or 88L) and allows the introduction of the end of a die blanket 114 therebetween.

The die is a thin flexible sheet or plate able to be bent to the diameter of cylinder 12 or 14 and is provided with a thickened edge 116 at the leading edge 16 and a similar thickened edge 118 at the trailing edge 18, as best shown in FIGS. 3 and 4. These thick edges 116 and 118 are the portions engaged by the clamping action and also serve as a failsafe provision in conjunction with the safety flange 90 should a clamp release occur in operation of the machine 10 or during a set-up of the die 114.

It is to be noted as shown in FIG. 2 that the trailing edge of the die 114 is provided with a centering rib 117 adjacent the thickened edge 118, which is used to line up the die 114 with a notch in the center clamp block 84T when the die is mounted on the cylinder.

The thickened edge 116 of the leading edge of the die blanket 114 has a pair of holes 120 and 122, with the latter hole 122 being elongated transversely. Hole 122 is engaged by a fixed dowel 124 as shown in FIG. 2 and the hole 120 by an adjustable dowel arrangement 126. Both dowels 124 and 126 extend from the bar 30.

The adjustable dowel 126 is housed in a bore 128 as best shown in FIGS. 9 and 10, and it consists of a rotatable spindle 130 having a dowel pin 134 protruding from an eccentrically bored hole 132. The spindle 130 is provided with a circumferential groove 138 by which it is retained in the bore 128 of clamping bar 30 with a snap ring 144. The snap ring 144 is contained in a shallow bore 140, as shown in FIGS. 2 and 9, which extends partly into the bore 128. This bore 140 has a groove 142. This groove 142 engages the snap ring 144 to the bar 30.

The spindle 130 is rotated by means of teeth 136 on its periphery which engage in worm gear manner with the threads of a setscrew type worm 148. This worm 148 is held captivated but free to rotate in a cross bore 146 by means of an ap'ertured lock screw 152 in a threaded counterbore 150. A wrench inserted through the lock screw 152 into the worm 148 will rotate the latter, which, in turn, rotates the spindle 130 and sweeps the dowel pin 134 in an eccentric path.

The clamping bar 30 is translatable lengthwise to a small degree by means of shifting mechanisms 154 and 156 at the right and left ends thereof, respectively. As shown in FIGS. 11 to 14 inclusive, this mechanism 154 or 156 works in a notched-out area 158 at each end of the clamping bar 30. This machining leaves an extended area 160. Further machining is done to finish a front plane surface 162 parallel to the rear face of the clamping bar 30.

A flat washer plate 168 bears against this surface 162 (FIGS. 11 and 12 only). A bolt 164 passes through a slot 170 in the plate 168, thence freely through a bell crank 172 and into a threaded hole 166 in drum 14. This hole 166 is near each end in the leading edge 16 of the drum 14 (or 12).

The depending leg 174 of a bell crank 172 has a spherical abutment 176 which may be the rounded point of a setscrew. The horizontal leg 178 of the bell crank 172 has an oval or rounded point adjustment screw threaded vertically therethrough. The rounded ends can thusly be brought to bear respectively at right angles against a hardened rest button 184. This rest button 184 mounts in a threaded hole 182 in the extended area 160 of the bar 30 and is there secured with a wrench engaged with wrenching holes 186.

Since the bell crank 172 is on a fixed pivot, namely bolt 164, in the drum 14, when its adjustment screw is tightened, the side pressure of abutment 176 against the rest button 184 causes the clamping bar 30 to shift relative to the drum 14 in a lateral direction.

In operation, as best shown in FIGS. 2 and 4, a die 114 in the form of a flexible sheet or plate is mounted to the drum 14 by camming the leading edge clamping mechanisms 36L of all the clamping and tensioning elements of the tensioning means 20. The leading edge of the die 114 is inserted into these open mouths and located over the dowel pins 124 and 126.

The camming latches 102 are then released which allows the clamping blocks 84T to move under their spring tension and hold the thickened edge 116 of the die 114 against the clamping bar 30.

At this point in the installation, the linkages 38 and 40 would be pressed inwardly, compressing spring 50 and held thusly by the cross-wise position of quarter turn screw 52.

The die 114 is then passed around the drum l4 and the trailing edge inserted into the similarly cammedopen trailing edge clamping mechanisms 36T. Normal procedure would be to close three of the latter clamping mechanisms 36T, one at each extreme edge and one at the center. These three associated linkages 38 and 40 are next released by the quarter turn screw 52, thus tensioning the die 114 under force of springs 50. Further tension may now be put on the die 114 by selecting other linkages 38 and 40 to similarly be clamped and released, thus removing wrinkles or bulges from the die 114 by opening and reclosing the originally used clamps 36T or 36L as required.

If the die 114 is skewed on the drum 14, the leading edge of the clamping bar 30 may be moved sideways with the bell cranks 172 in correction of the condition.

After satisfactory positioning and clamping of the die 114, the quarter turn screw 52 are all rotated to parallelism with the linkages and the springs 50 all functioning to maintain the die 114 under tension during use, which force resolves to the take-up distance indicated at the bottom of FIG. 4.

Obviously many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. In a rotating cylinder impression machine, a device for clamping and tensioning the ends of a die sheet on a cylinder, comprising in combination with a cylinder having a leading edge relative to its rotational direction and defining the position to be occupied by the first end of said die sheet and a trailing edge defining the position to be occupied by the opposite end of said die sheet, said cylinder having a leading edge cutout portion, a trailing edge cutout portion, and a flat cutout portion positioned between said leading and trailing edge cutout portions, all the said cutout portions extending substantially axially across the cylinder, the clamping and tensioning device bridging said flat cutout portion and lying below the periphery of the cylinder between the positions occupied by the ends of the die sheet and within the space defined by the cutout portions and further being secured to the cylinder, the clamping and tensioning device further comprising:

a stationary clamping bar disposed within the leading edge cutout portion of the cylinder and secured thereto, the bar having a radially facing clamping surface fitting flushly with the perimetric surface of the cylinder;

at least one pivotally movable clamp bar disposed within the trailing edge cutout portion of the cylinder and pivotally attached thereto, the bar having a radially facing clamping surface;

first clamping means opposing the clamping surface of the clamping bar and including spring means held between the clamping bar and said first clamping means and biasing saidclamping means toward the clamping surface of the clamping bar for tensionably holding the first end ofthe die sheet therebetween;

second clamping means opposing the clamping surface of the movable clamp bar and including spring means held between the movalbe clamp bar and said second clamping means and biasing said clamping means toward the clamping surface of the clamping bar for tensionably holding the second end of the die sheet therebetween;

first link means pivotally connected to the first clamping means and extending transversely of the cylinder toward the second clamping means;

second link means pivotally connected to the second clamping means and extending transversely of the cylinder toward the first clamping means and connecting pivotally with the first link means medially of the flat cutout portion of the cylinder;

hinge means hingeably connecting the first and second link means at their respective inner ends for articulating the said link means relative to each other to allow the pivotally joined inner ends of the link means to be movable outwardly from the cylinder in a radial direction; and,

coil spring means housed within the cylinder and extending radially from therewithin to abut and act against the first and second link means at substantially the hinged juncture thereof, the coil spring means biasing the hinged ends of the said link means outwardly from the cylinder in a radial direction, thereby to bias the first and second clamping means toward each other in substantially a circumferential direction to tension the die sheet on the cylinder.

2. The clamping and tensioning device of claim 1 and further comprising:

means for holding the first and second link means against the flat cutout portion of the cylinder.

3. The clamping and tensioning device of claim 1 wherein the stationary clamping bar extends lengthwise of the cylinder over subsantially the full length thereof and wherein a plurality of the pivotally movable clamp bars are disposed at spaced intervals within the trailing edge cutout portion of the cylinder, each of the movable clamp bars having one of said second clamping means disposed oppositely therefrom.

4. The clamping and tensioning device of claim 1 wherein the first end of the die sheet is formed with hole means and the device further comprises dowel means disposed on the stationary clamping bar and being received within the hole means in the die sheet to maintain the die sheet in a desired position relative to the stationary clamping bar.

5. The clamping and tensioning device of claim 4 wherein the dowel means includes an adjustable dowel mechanism housed substantially within a bore means in the stationary clamping bar and comprising:

a rotatable spindle having an eccentrically bored hole disposed longitudinally therein, the spindle also having a circumferential groove disposed in its outer end and further having teeth about the periphery thereof, the spindle being disposed in the aforesaid bore means in the stationary clamping bar with the outer end of the spindle located in the upper portion of the bore;

a dowel pin disposed in the eccentrically bored hole and protruding therefrom, the pin extending from the bore means in the stationary clamping bar;

a snap ring fitting into a portion of the circumferential groove disposed in the spindle, the snap ring being held within a shallow portion of the bore means contiguous to that portion of the bore means in which the spindle is held; and,

worm gear means disposed in the stationary clamping bar and engaging the teeth on the rotatable spindle, rotationvof the worm gear means acting to rotate the spindle and to sweep the dowel pin in an eccentric path, thereby to move the dowel pin within the hole means in the die sheet during placement and removal of the die sheet from the cylinder.

6. The clamping and tensioning device of claim 1 wherein the stationary clamping bar has notched-out portions at each end thereof and bar lateral translation means disposed in each of the notched-out portions, the translation means each comprising:

8. wherein the pivotally movable clamp bar comprises:

opposed hinge brackets secured to the trailing edge 'plate means bearing against the innermost surface of the notched-out portion;

bellcrank means of substantially L-shaped conformation disposed between the plate means and that surface of the leading edge cutout portion which is parallel to the plate means, the bellcrank means being pivotally held therebetwen at the elbow portion thereof, the bellcrank means having a substantially horizontally disposed arm member and a substantially vertically disposed arm member;

button means disposed on the lower surface of the notched-out portion; and,

stationary pressure means disposed on one of the arm members and adjustable pressure means disposed on the other of the arm members, the respective pressure means bearing on adjacent surfaces of the button means and at right angles relatively thereto. movement of the adjustable pressure means toward or away from the button means causing the lateral pressure exerted on the button means by the stationary pressure means to respectively increase or decrease, thereby to cause the clamping bar to be laterally movable relative to the cylinder.

7. The clamping and tensioning device ofclaim l and further comprising:

camming means surmounting both the first and second clamping means and rotatable to bias the said clamping means away from respective clamping surfaces of the stationary clamping bar and movable clamp bar, thereby allowing the respective ends of the die sheet to be positioned between or removed from between the said clamping means and the said clamping surfaces.

The clamping and tensioning device of claim 1 cutout portion of the cylinder and having oppositely facing and aligned bores disposed therein; and,

aligned hinge pin means on opposite sides of a narrowed rear portion of the clamp bar, the hinge pin means being received within the oppositely facing and aligned bores in the hinge brackets, the clamp bar being pivotally movable about the hinge pin means.

9. The clamping and tensioning device of claim 8 wherein the first clamping means comprise:

spaced side plates secured to the stationary clamp bar, each of the side plates having diagonally disposed holes formed therein and aligning with corresponding holes in the opposing side plate, and further having an additional pair of aligned holes in the forwardmost portions thereof; and,

a clamping block having hinge pins extending from opposite sides thereof and received rotatably within one pair of aligned holes in the spaced side plates, thereby to allow said clamping block to pivot thereabout, the clamping block having a nose member on the outermost portion thereof and which confronts the clamping surface on the stationary clamping bar, the spring means being disposed between the rear portion of the clamping block and the stationary clamp bar and acting to bias the nose member of the clamping block toward the clamping surface of the clamping bar.

10. The clamping and tensioning device of claim 9 and further comprising camming means surmounting the first clamping means and including a T-shaped latch having aligned hinge pins extending from the arms of the latch, the pins being received in a second pair of the holes in the side plates of the first clamping means, the latch being rotatable about the hinge pins, the latch further having a camming surface formed on the rear portion of the arms and engageable with said clamping means on rotation of the latch about the hinge pins to bias the nose member of the clamping block away from the clamping surface of the clamping bar.

11. The clamping and tensioning device of claim 10 wherein the second clamping means comprise:

spaced side plates secured to the movable clamping bar, each of the side plates having diagonally disposed holes formed therein and aligning with corresponding holes in the opposing side plate, and further having an additional pair of aligned holes in the forwardmost portions thereof; and, a clamping block having hinge pins extending from opposite sides thereof and received rotatably within one pair of aligned holes in the spaced side plates, thereby to allow said clamping block to pivot thereabout, the clamping block having a nose member on the outermost portion thereof and which confronts the clamping surface on the movable clamping bar, the spring means being disposed between the rear portion ofthe clamping block and the movable clamping bar and actingto bias the nose member of the clamping block toward the clamping surface of said clamp bar.

12. The clamping and tensioning device of claim 11 and further comprising camming means surmounting the second clamping means and including a T-shaped latch having alinged hinge pins extending from the arms of the latch, the pins being received in a second pair of the holes in the side plates of the second clamping means, the latch being rotatable about the hinge pins, the latch further having a camming surface formed on the rear portion of the arms and engageable with said clamping means on rotation of the latch about the hinge pins to bias the nose member ofthe clamping block away from the clamping surface of the clamping bar.

13. The clamping and tensioning device of claim 12 wherein the first link means are pivotally hinged to the side plates secured to the stationary clamp bar within the additional pair of aligned holes in the forwardmost portions thereof and the second link means are pivotally hinged to the side plates secured to the movable clamping bar within the additional pair of aligned holes in the forwardmost portion thereof,

14. The clamping and tensioning device of claim 13 wherein a plurality of said pivotally movable clamp bars, first and second clamping means, first and second link means, hinge means, and coil spring means are provided, each combination thereof being laterally spaced from each other such that selected portions of the ends of the die sheet can be independently clamped and moved toward each other thereby.

15. The clamping and tensioning device of claim 14 and further comprising means for securing said first and second link means in a position whereby the link means are substantially parallel and in a eo-linear condition so as to maintain said first and second clamping means respectively apart from the stationary clamping bar and the movable clamp bars.

16. The clamping and tensioning device of claim 15 and further comprising means for releasing each pair of said first and second link means independently from the ends of the die sheet. 

1. In a rotating cylinder impression machine, a device for clamping and tensioning the ends of a die sheet on a cylinder, comprising in combination with a cylinder having a leading edge relative to its rotational direction and defining the position to be occupied by the first end of said die sheet and a trailing edge defining the position to be occupied by the opposite end of said die sheet, said cylinder having a leading edge cutout portion, a trailing edge cutout portion, and a flat cutout portion positioned between said leading and trailing edge cutout portions, all the said cutout portions extending substantially axially across the cylinder, the clamping and tensioning device bridging said flat cutout portion and lying below the periphery of the cylinder between the positions occupied by the ends of the die sheet and within the space defined by the cutout portions and further being secured to the cylinder, the clamping and tensioning device further comprising: a stationary clamping bar disposed within the leading edge cutout portion of the cylinder and secured thereto, the bar having a radially facing clamping surface fitting flushly with the perimetric surface of the cylinder; at least one pivotally movable clamp bar disposed within the trailing edge cutout portion of the cylinder and pivotally attached thereto, the bar having a radially facing clamping surface; first clamping means opposing the clamping surface of the clamping bar and including spring means held between the clamping bar and said first clamping means and biasing said clamping means toward the clamping surface of the clamping bar for tensionably holding the first end of the die sheet therebetween; second clamping means opposing the clamping surface of the movable clamp bar and including spring means held between the movalbe clamp bar and said second clamping means and biasing said clamping means toward the clamping surface of the clamping bar for tensionably holding the second end of the die sheet therebetween; first link means pivotally connected to the first clamping means and extending transversely of the cylinder toward the second clamping means; second link means pivotally connected to the second clamping means and extending transversely of the cylinder toward the first clamping means and connecting pivotally with the first link means medially of the flat cutout portion of the cylinder; hinge means hingeably connecting the first and second link means at their respective inner ends for articulating the said link means relative to each other to allow the pivotally joined inner ends of the link means to be movable outwardly from the cylinder in a radial direction; and, coil spring means housed within the cylinder and extending radially from therewithin to abut and act against the first and second link means at substantially the hinged juncture thereof, the coil spring means biasing the hinged ends of the said link means outwardly from the cylinder in a radial direction, thereby to bias the first and second clamping means toward each other in substantially a circumferential direction to tension the die sheet on the cylinder.
 1. In a rotating cylinder impression machine, a device for clamping and tensioning the ends of a die sheet on a cylinder, comprising in combination with a cylinder having a leading edge relative to its rotational direction and defining the position to be occupied by the first end of said die sheet and a trailing edge defining the position to be occupied by the opposite end of said die sheet, said cylinder having a leading edge cutout portion, a trailing edge cutout portion, and a flat cutout portion positioned between said leading and trailing edge cutout portions, all the said cutout portions extending substantially axially across the cylinder, the clamping and tensioning device bridging said flat cutout portion and lying below the periphery of the cylinder between the positions occupied by the ends of the die sheet and within the space defined by the cutout portions and further being secured to the cylinder, the clamping and tensioning device further comprising: a stationary clamping bar disposed within the leading edge cutout portion of the cylinder and secured thereto, the bar having a radially facing clamping surface fitting flushly with the perimetric surface of the cylinder; at least one pivotally movable clamp bar disposed within the trailing edge cutout portion of the cylinder and pivotally attached thereto, the bar having a radially facing clamping surface; first clamping means opposing the clamping surface of the clamping bar and including spring means held between the clamping bar and said first clamping means and biasing said clamping means toward the clamping surface of the clamping bar for tensionably holding the first end of the die sheet therebetween; second clamping means opposing the clamping surface of the movable clamp bar and including spring means held between the movalbe clamp bar and said second clamping means and biasing said clamping means toward the clamping surface of the clamping bar for tensionably holding the second end of the die sheet therebetween; first link means pivotally connected to the first clamping means and extending transversely of the cylinder toward the second clamping means; second link means pivotally connected to the second clamping means and extending transversely of the cylinder toward the first clamping means and connecting pivotally with the first link means medially of the flat cutout portion of the cylinder; hinge means hingeably connecting the first and second link means at their respective inner ends for articulating the said link means relative to each other to allow the pivotally joined inner ends of the link means to be movable outwardly from the cylinder in a radial direction; and, coil spring means housed within the cylinder and extending radially from therewithin to abut and act against the first and second link means at substantially the hinged juncture thereof, the coil spring means biasing the hinged ends of the said link means outwardly from the cylinder in a radial direction, thereby to bias the first and second clamping means toward each other in substantially a circumferential direction to tension the die sheet on the cylinder.
 2. The clamping and tensioning device of claim 1 and further comprising: means For holding the first and second link means against the flat cutout portion of the cylinder.
 3. The clamping and tensioning device of claim 1 wherein the stationary clamping bar extends lengthwise of the cylinder over subsantially the full length thereof and wherein a plurality of the pivotally movable clamp bars are disposed at spaced intervals within the trailing edge cutout portion of the cylinder, each of the movable clamp bars having one of said second clamping means disposed oppositely therefrom.
 4. The clamping and tensioning device of claim 1 wherein the first end of the die sheet is formed with hole means and the device further comprises dowel means disposed on the stationary clamping bar and being received within the hole means in the die sheet to maintain the die sheet in a desired position relative to the stationary clamping bar.
 5. The clamping and tensioning device of claim 4 wherein the dowel means includes an adjustable dowel mechanism housed substantially within a bore means in the stationary clamping bar and comprising: a rotatable spindle having an eccentrically bored hole disposed longitudinally therein, the spindle also having a circumferential groove disposed in its outer end and further having teeth about the periphery thereof, the spindle being disposed in the aforesaid bore means in the stationary clamping bar with the outer end of the spindle located in the upper portion of the bore; a dowel pin disposed in the eccentrically bored hole and protruding therefrom, the pin extending from the bore means in the stationary clamping bar; a snap ring fitting into a portion of the circumferential groove disposed in the spindle, the snap ring being held within a shallow portion of the bore means contiguous to that portion of the bore means in which the spindle is held; and, worm gear means disposed in the stationary clamping bar and engaging the teeth on the rotatable spindle, rotation of the worm gear means acting to rotate the spindle and to sweep the dowel pin in an eccentric path, thereby to move the dowel pin within the hole means in the die sheet during placement and removal of the die sheet from the cylinder.
 6. The clamping and tensioning device of claim 1 wherein the stationary clamping bar has notched-out portions at each end thereof and bar lateral translation means disposed in each of the notched-out portions, the translation means each comprising: plate means bearing against the innermost surface of the notched-out portion; bellcrank means of substantially L-shaped conformation disposed between the plate means and that surface of the leading edge cutout portion which is parallel to the plate means, the bellcrank means being pivotally held therebetwen at the elbow portion thereof, the bellcrank means having a substantially horizontally disposed arm member and a substantially vertically disposed arm member; button means disposed on the lower surface of the notched-out portion; and, stationary pressure means disposed on one of the arm members and adjustable pressure means disposed on the other of the arm members, the respective pressure means bearing on adjacent surfaces of the button means and at right angles relatively thereto, movement of the adjustable pressure means toward or away from the button means causing the lateral pressure exerted on the button means by the stationary pressure means to respectively increase or decrease, thereby to cause the clamping bar to be laterally movable relative to the cylinder.
 7. The clamping and tensioning device of claim 1 and further comprising: camming means surmounting both the first and second clamping means and rotatable to bias the said clamping means away from respective clamping surfaces of the stationary clamping bar and movable clamp bar, thereby allowing the respective ends of the die sheet to be positioned between or removed from between the said clamping means and the said clamping surfaces.
 8. The clamping and tensioning device of claim 1 Wherein the pivotally movable clamp bar comprises: opposed hinge brackets secured to the trailing edge cutout portion of the cylinder and having oppositely facing and aligned bores disposed therein; and, aligned hinge pin means on opposite sides of a narrowed rear portion of the clamp bar, the hinge pin means being received within the oppositely facing and aligned bores in the hinge brackets, the clamp bar being pivotally movable about the hinge pin means.
 9. The clamping and tensioning device of claim 8 wherein the first clamping means comprise: spaced side plates secured to the stationary clamp bar, each of the side plates having diagonally disposed holes formed therein and aligning with corresponding holes in the opposing side plate, and further having an additional pair of aligned holes in the forwardmost portions thereof; and, a clamping block having hinge pins extending from opposite sides thereof and received rotatably within one pair of aligned holes in the spaced side plates, thereby to allow said clamping block to pivot thereabout, the clamping block having a nose member on the outermost portion thereof and which confronts the clamping surface on the stationary clamping bar, the spring means being disposed between the rear portion of the clamping block and the stationary clamp bar and acting to bias the nose member of the clamping block toward the clamping surface of the clamping bar.
 10. The clamping and tensioning device of claim 9 and further comprising camming means surmounting the first clamping means and including a T-shaped latch having aligned hinge pins extending from the arms of the latch, the pins being received in a second pair of the holes in the side plates of the first clamping means, the latch being rotatable about the hinge pins, the latch further having a camming surface formed on the rear portion of the arms and engageable with said clamping means on rotation of the latch about the hinge pins to bias the nose member of the clamping block away from the clamping surface of the clamping bar.
 11. The clamping and tensioning device of claim 10 wherein the second clamping means comprise: spaced side plates secured to the movable clamping bar, each of the side plates having diagonally disposed holes formed therein and aligning with corresponding holes in the opposing side plate, and further having an additional pair of aligned holes in the forwardmost portions thereof; and, a clamping block having hinge pins extending from opposite sides thereof and received rotatably within one pair of aligned holes in the spaced side plates, thereby to allow said clamping block to pivot thereabout, the clamping block having a nose member on the outermost portion thereof and which confronts the clamping surface on the movable clamping bar, the spring means being disposed between the rear portion of the clamping block and the movable clamping bar and acting to bias the nose member of the clamping block toward the clamping surface of said clamp bar.
 12. The clamping and tensioning device of claim 11 and further comprising camming means surmounting the second clamping means and including a T-shaped latch having alinged hinge pins extending from the arms of the latch, the pins being received in a second pair of the holes in the side plates of the second clamping means, the latch being rotatable about the hinge pins, the latch further having a camming surface formed on the rear portion of the arms and engageable with said clamping means on rotation of the latch about the hinge pins to bias the nose member of the clamping block away from the clamping surface of the clamping bar.
 13. The clamping and tensioning device of claim 12 wherein the first link means are pivotally hinged to the side plates secured to the stationary clamp bar within the additional pair of aligned holes in the forwardmost portions thereof and the second link means are pivotally hinged to the side plates secured to the movable clamping bar within the additional pair of Aligned holes in the forwardmost portion thereof.
 14. The clamping and tensioning device of claim 13 wherein a plurality of said pivotally movable clamp bars, first and second clamping means, first and second link means, hinge means, and coil spring means are provided, each combination thereof being laterally spaced from each other such that selected portions of the ends of the die sheet can be independently clamped and moved toward each other thereby.
 15. The clamping and tensioning device of claim 14 and further comprising means for securing said first and second link means in a position whereby the link means are substantially parallel and in a co-linear condition so as to maintain said first and second clamping means respectively apart from the stationary clamping bar and the movable clamp bars. 